As examples of the vibration-type actuator described above, various vibration-type actuators that linearly drive a driven member have been proposed. For example, PTL 1 proposes a vibration-type actuator, whose driving principle will be described with reference to FIG. 5 and FIGS. 6A and 6B. As illustrated in FIG. 5, a vibrator includes a rectangular elastic body 106 (vibrator in PTL 1) and an electromechanical transducer 107 bonded thereto.
FIGS. 6A and 6B illustrate two bending vibration modes of the vibrator. The vibration mode illustrated in FIG. 6A is one of the two bending vibration modes (hereinafter referred to as mode A). Mode A provides a second-order bending vibration in a long-side direction of the rectangular elastic body 106 (indicated by arrow X). The vibration in mode A has three nodes parallel to a short-side direction of the elastic body 106 (indicated by arrow Y). Protrusions 108 are disposed near the nodes of vibration in mode A. The protrusions 108 reciprocate in the direction of arrow X in response to vibration in mode A.
The vibration mode illustrated in FIG. 6B is the other of the two bending vibration modes (hereinafter referred to as mode B). Mode B provides a first-order bending vibration in the short-side direction of the rectangular elastic body 106 (indicated by arrow Y). The vibration in Mode B has two nodes parallel to the long-side direction of the elastic body 106 (indicated by arrow X). The nodes in mode A and the nodes in mode B are substantially orthogonal to each other in the XY plane. The protrusions 108 are disposed near antinodes of vibration in mode B. The protrusions 108 reciprocate in the direction of arrow Z in response to vibration in mode B.
When the vibrations in modes A and B are generated with a predetermined phase difference, an elliptical motion takes place at end portions of the protrusions 108. A slider 116 serving as a driven member is configured to be brought into pressure contact with the end portions of the protrusions 108. The slider 116 can be moved relative to the elastic body 106 in the direction of arrow L by the elliptical motion of the prorusions 108.
In this vibration-type actuator, the driven member is brought into pressure contact with the vibrator that vibrates, so that the driven member performs relative motion in response to the vibration. As a result, it is possible that abnormal noise will occur when the driven member bounces as the vibrator vibrates. It is also possible that relative movement of the driven member will become unstable.
A configuration that addresses these problems will be described with reference to FIGS. 7A and 7B. As illustrated, the elastic body 106 has protrusions 108 and an attached portion to which the electromechanical transducer 107 is attached. The protrusions 108 each have a contact portion to be in contact with a driven member, and a spring portion between the contact portion and the attached portion. The spring portion is provided to give elasticity to the protrusion 108 when the contact portion is pressed by contact with the driven member. A space is created between the contact portion of each protrusion 108 and the electromechanical transducer 107 joined to the protrusions 108. The protrusions 108 each have a standing portion that connects the contact portion to the spring portion. As the spring portion, a spring portion is formed to be thinner than the contact portion, the standing portion, and the attached portion. Thus, when the contact portions of the protrusions 108 are pressed by contact with the driven member, the spring portions are elastically deformed, so that the elastic body 106 exhibits elasticity. This improves stability in relative movement of the elastic body 106 and the driven member.